How to use sed to replace only the first occurrence in a file?

Question

I would like to update a large number of C++ source files with an extra include directive before any existing #includes. For this sort of task, I normally use a small bash s

Answer 1

Using FreeBSD ed and avoid ed's "no match" error in case there is no include statement in a file to be processed:

teststr='
#include 
#include 
#include 
'

# using FreeBSD ed
# to avoid ed's "no match" error, see
# *emphasized text*http://codesnippets.joyent.com/posts/show/11917 
cat <<-'EOF' | sed -e 's/^ *//' -e 's/ *$//' | ed -s <(echo "$teststr")
   H
   ,g/# *include/u\
   u\
   i\
   #include "newfile.h"\
   .
   ,p
   q
EOF